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Multi-Way Conventional loudspeakers with crossovers

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Old 30th October 2012, 09:38 PM   #51
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Quote:
Originally Posted by theaudiophile View Post
PIPEDREAMS by Nearfield Acoustics

what about these speakers? These are very tall yet they did not sound like a multi way with 100 drive units. Why?
Why should they?
They are much taller than mine that create nice uniform stereo image, and I don't hear them. However, their tweeters are different. My Forters have flat surfaces, like some kind of light metal(?) foam, on thin rubber suspension, 1 inch high.

Click the image to open in full size.


This picture was taken in my walk in closet using Behringer mike, the speaker was hanging on wires:

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Old 31st October 2012, 12:12 AM   #52
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Quote:
Originally Posted by theaudiophile View Post
PIPEDREAMS by Nearfield Acoustics

what about these speakers? These are very tall yet they did not sound like a multi way with 100 drive units. Why?
Dominant factor is wavelength v cone diameter. And as source spacing decreases, frequency increases at which two sources may be resolved. Somewhere 1/4 or 1/3 of a wavelength source spacing it becomes very difficult to resolve system as 1 or 2 sources.

This is underlying principle of driver coupling with line sources. In case of effective floor to ceiling line source a cylindrical wavefront. If each element of array has flat response on axis and falls as it must, then sum of responses at a listening point is not flat; thus line sources have specific equalization needs.

Keele has multiple papers with details on line sources.


In two way line source crossover lobing is in horizontal plane and will show up in off axis measurements, with all the usual dependencies of sealed, OB, angular separation v frequency etc.

Looking at Pipedreams: How it works indicates crossovers at 60Hz and 6kHz. With pairing of 4" and 1" drivers on flat face baffle, estimating their centers at 3" apart, 1.125" as half wavelength for 6kHz guarantees several horizontal lobes that are modified by off axis directive behavior of drivers.

Pipedreams require dedicated active crossover that also does some form of EQ.

All that driver area does improve linearity and accompanying reductions in IMD.

My Pluto style speaker has 5.24" and 2" drivers with about 3.75" of vertical separation; <1/3 a wavelength for 1kHz crossover. The off axis response follow directive behavior of tweeter both horizontally and vertically:

Click the image to open in full size.

Bang for the buck isn't Pipedream.

Andrew
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